Megger SCT-MMA, User Manual, Page: 17 / 37

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PREPARING TO TEST
UNDERSTANDING TEST METHODS
Test method defines how the reference power measurement is performed. Test methods are defined by the standards bodies. The
standards do not use consistent naming to define the same test methods. In this manual the methods are referred to as Test Method A, B
and C. Please refer to Appendix A for some common standard test method naming and defined method use.
 Test Method A – (two reference cord measurement)
Setting a reference using test method A requires two reference patch cords and one adapter. The measurement results include
the loss of the cable plant and the loss of one connection.
 Test Method B – (one reference cord measurement)
Setting a reference using test method B requires one reference patch cords and no adapters. The measurement results include
the loss of the cable plant and the loss of two connections.

Test Method C – (three reference cord measurement)
Setting a reference using test method C requires three reference patch cords, and two adapters. The measurement results
include the loss of the cable plant only.
If you are testing fiber optic links with connectors other than SC style, refer to Appendix B for the Modified Test Method B that produces
Test Method B results.
ESTABLISHING A FIBER OPTIC REFERENCE
Setting a fiber optic reference establishes the zero loss power and zero length distance for all future measurements. Setting a reference also
removes additional losses due to reference patch cords and adapters that should not be included in the measurement. Therefore properly
setting a reference is necessary for obtaining accurate results.
Establish a fiber optic reference only after the SCT Primary and Secondary units and the SCT-MMA/SMA fiber optic adapters
have been on for five minutes. Allow additional time for the adapter to reach ambient temperature if the adapters have been
stored above or below ambient temperature.
The reference measurement is invalidated if the reference patch cord is disconnected from the SCT_MMA/SMA fiber optic
adapter. Disconnecting and re-connecting a reference patch cord will alter the optical characteristics resulting in a different
reference loss power.
Establish a new reference:
 Anytime the SCT-MMA/SMA adapters are attached.
 Anytime the reference patch cords are disconnected from the SCT-MMA/SMA adapters.

Anytime negative loss or length results are obtained.
The SCT will request a new reference:
 After a 24 hour period has elapsed since the last reference
 Anytime a different fiber optic is attached to the primary or secondary SCT.

Anytime the test mode is switched from loopback to secondary or secondary to loopback.

Anytime the test method is changed.